A Certain Heroic Spirit
by Ultimate Warrior of Zera
Summary: Zouken's plans go astray when he accidentally summons a Servant from a certain world. One-shot.


**Author's Note:** This fic is inspired by elements from a few fics, including God Slaying Blade Works by Marcus Galen Sands (mostly the Fourth Holy Grail War omakes) and Fate/Stay Night: Ultimate Master by Ten-Faced Paladin (damn I wish that story hadn't been abandoned). Note this is a one shot and I have no plans for advancing past what I write here, as I have no idea how I would do it.

* * *

Zouken Matou was greatly displeased. His familiars had been observing all the battles between Masters and Servants so far, and he was deeply regretting his decision to allow his grandson to usurp control over his granddaughter's Servant. Sakura may have lacked the drive to fight, but Shinji was both a fool and his lack of magic severely crippled Rider's power, rendering her chances of victory nil. It was disgraceful that an amateur Magus like Shirou Emiya was actually able to fend her off, considering humans are supposed to be no match for Servants, even if he needed to be rescued in the end. He considered disposing of Shinji and using his Crest Worms to assume direct control of Sakura in order to command Rider at full strength, but then he noticed something. Servant Assassin was actually a pseudo Servant summoned by Caster, and completely ineligible to win the Holy Grail. There may be a chance to join the Holy Grail War himself, and obtain the true immortality he had sought for so long…

That night, he called Sakura, Shinji, and Rider to the basement of the Matou household and told them of his plan to summon a True Assassin to team up with Rider and increase their chances of winning the Holy Grail War. Shinji, cradling the Book of the False Attendant, sneered and told the old man to do what he wanted. Rider simply nodded and Sakura meekly nodded as well. Zouken crafted the summoning circle and spoke the chant to summon a Servant, using the very word "Assassin" as the catalyst. And that was when things went wrong.

The first sign was that the three Command Spells that appeared on Zouken's right hand resembled a dragon's head. The second was that the figure who appeared in the summoning circle did not resemble any of the 19 variants of Hassan-i-Sabbah, The Old Man in the Mountain, at all. He was a Japanese boy about seventeen years in appearance, but his eyes were the hardened ones of a veteran of countless battles and suffering. He was about 168 cm tall, an average height. His black hair was spiky. He wore sneakers, black jeans, a white shirt, and a black jacket with a hood. Zouken, Sakura, and Shinji were all taken aback by his appearance, as he looked like an ordinary boy from the modern world instead of a legendary hero of old. Although Rider was blindfolded, she raised her head in surprise, as while she could tell he was there, he was like a void, as if there was no prana to sense. Yet somehow, she also felt an overwhelming instinctual fear telling her that this person was extremely dangerous. Zouken attempted to see his Servant's stats, only for the sheet to be blank. The boy turned to Zouken and spoke.

"Servant Avenger has answered your summons. I ask of you: Are you my Master?"

Zouken struggled to compose himself. He vaguely remembered an Avenger being summoned for the Third Holy Grail War, but that was over 70 years ago.

"Servant Avenger? I called upon Servant Assassin."

"Sorry to disappoint you, but that spot must be already filled. A Holy Grail War only needs seven Servants to begin. When the usual seven spots are filled, any more summonings call upon alternate Classes. Avengers are considered anti heroes. They did their deeds either filled with hatred and rage, or inspiring it in others. I did the latter. No matter how many people I saved or inspired, there were so many who hated me, either out of jealousy, fear, or my challenging the status quo. In my hometown, I was hated just for existing, long story. Also, I never let rules or the law stop my path, and one time, I even willingly became the enemy of the entire world, just to protect the smile of a single girl."

He looked wistful for a second, then shrugged.

"Based on my skills and what I had done in life, I believe I would also qualify for Assassin, Berserker, or Shielder. That may be why I was summoned if you were trying to get Assassin, but that's irrelevant now."

Zouken cleared his throat and indicated the others in the room.

"Indeed. I am your Master, Zouken Matou. Servant Rider and her Masters shall be our allies for the time being."

Avenger turned to the other three, and he smiled and his eyes lit up when he beheld Rider standing protectively next to Sakura. In life, he always did like Cool Big Sis type girls.

"Our pact is sealed then. We will all work together. But first, I need to check something."

To their surprise, he astralized and moved upstairs. Rider prepared for an attack, but after half a minute, Avenger returned to his original spot and took solid form again.

"Sorry about that. I just wanted to check your calender and globe to confirm something. I felt that the knowledge the Grail gave me to fit into this world felt strange, and now I see way. It's the year 2004? That was the year my legend began, when I did my first great deed. I died peacefully of old age in 2081. At first, I assumed that I had been summoned from the future, but then I looked at your globe and both my hometown and the city where I lived for most of my teens do not exist, plus certain cities I remember are either different or missing. I can only conclude that I was summoned from an alternate universe. Oh well, at the very least, I won't run into my past self or my old friends."

Zouken was intrigued.

"The Holy Grail accessed the Second Magic when summoning you? Wait, I have other questions. Why can I not sense your prana or see your stats and skills?"

Before Avenger could answer, Shinji gave an obnoxious laugh.

"Probably because he doesn't have any skills! I read up on that journal you wrote about the Third Holy Grail War, Grandpa. The last time Avenger was summoned, he was a total wuss and got himself killed in an instant! This guy is a dud and we don't need him. Rider, take him-"

"STOP!"

Avenger had cut him off.

"You can't sense me because my Noble Phantasm prevents it. Now, I've dealt with critics my whole life, kid. I never really cared what they thought and just let my actions do the talking. Rest assured that I am nothing like that Avenger you are talking about. And even if I didn't have powers, while I look like a teen, I have memories of 94 years of life, and most of it was fighting and winning against people a lot stronger and experienced than me. Admittedly, I kinda wish I had been summoned as Assassin. Maybe then I would be in my adult body where I had a pretty sweet bulletproof vest, machete, katana, and guns, but beggars can't be choosers. Now kid, how good a fighter are you?"

Shinji was taken aback, then growled and backed away, gritting his teeth. Zouken sneered at his idiot grandson being put in his place. Rider gave a sneaky smile, grateful that the abusive, false Master she was forced to serve was hurt in the worst way possible, his ego. However, the ever compassionate Sakura approached Shinji and tried to comfort her adoptive brother.

"Please calm down, Shinji-"

"Shut up!"

In a rage, he backhanded her. Rider quickly caught her before she hit the ground, but did nothing else but glare at Shinji, angry at the Command Spell that prevented her from attacking him. Zouken looked on apathetically; he had seen Shinji's abuse many times and didn't care, as long as Sakura wasn't maimed and remained useful for his plans. Avenger on the other hand…

"You bastard!"

Enraged, he lunged at Shinji incredibly fast, prepping his right fist. Normally, Rider would have immediately moved to intercept him, but since she was holding Sakura, she chose to protect her true Master and moved her behind her. Shinji shrieked like a little girl and desperately held up the Book of the False Attendant like a shield. However, as soon as Avenger's fist made contact with the book, there was a peculiar sound, like both a camera flash going off and glass shattering, then the book completely disintegrated. The fist continued and impacted Shinji's cheek, instantly launching him into the wall, unconscious and with a huge bruise.

Before Sakura could process this, she looked down in surprise as her two remaining Command Spells returned to her hand (having used up one to create the Book of the False Attendant for Shinji's use). Rider silently rejoiced at feeling her full strength return to her now that Sakura was her Master again and properly supplying her with prana and knew she was in Avenger's debt, even if he did not understand what he had just done.

After calming down, Avenger turned around and after making sure Rider wasn't going to attack him, bowed to Zouken.

"Apologies, Master. I acted without thinking."

Zouken chuckled.

"No need for that. I believe you've all done us a favor. Shinji was nothing but a liability with his stupidity and weakness. Since you destroyed that book, Rider is now back to full power now that she is with her original Master. By the way, how did you do that?"

"My Noble Phantasm, Imagine Breaker, allows my right hand to negate and destroy anything supernatural with a touch."

Zouken, Sakura, and Rider were all taken aback by this. Rider backed away from Avenger terrified.

"Rider, please relax. I won't attack you unless you force me to. I'm still for this alliance. Besides, Imagine Breaker won't kill Servants unless they aren't being fed prana by their Masters. The worst it would do to you is destroy your clothes and nullify your powers until I let go."

Zouken considered what he had heard. His Servant had perhaps the most powerful Noble Phantasm he had ever witnessed.

"Sakura, my dear. Now that Shinji can no longer act as your proxy, you have no choice but to participate in the Grail War. Is that understood?"

Sakura sighed and bowed her head.

"Yes, Grandpa. I understand."

Rider put a comforting hand on her shoulder. Avenger smiled.

"Wonderful! Now, before we join the war, I'm going to need a blade."

Zouken raised an eyebrow.

"What for?"

"None of my Noble Phantasms are actual weapons. Fortunately, I can turn anything I hold into a Noble Phantasm."

Zouken chuckled, remembering his amusing failure of a son, Kariya, and his Servant.

"Wow, that takes me back. The Berserker of the previous Grail War had a similar ability. Very well. I have a tradition katana adorning my home. You may use it."

"Thank you Master."

After Zouken told him where it was, Avenger swiftly retrieved it and returned to the basement holding it with his left hand. The three could sense that he was telling the truth; the ordinary blade had become a Noble Phantasm able to kill a Servant.

"This will do nicely."

Avenger sheathed it and wore it on his right side, so that he could draw it with his left hand.

Zouken rubbed his hands together.

"One last thing. It is time to dispose of the trash."

He unleashed a swarm of his worms, which crawled towards the unconscious Shinji, intent on devouring him. Sakura shrieked, remembering her unspeakable experiences with the worms. Rider stood in front of her and drew her chain blades in case the worms tried to attack her. Before the worms could reach Shinji, Avenger jumped in the way and swept his right hand through them. Every worm he touched disintegrated, while the rest fled in fear.

"Master, I cannot allow this. Even if he's an asshole, would you really kill your own grandson?"

"Oh please, if you knew what this boy had been up to, you'd be begging me to kill him."

Zouken held his hand up and one of the Command Spells vanished.

"By my Command Spell, you can never oppose me again, Avenger!"

Avenger grunted in shock as he found he was unable to move towards Zouken. The worms started moving towards Shinji again. Sakura was beside herself. In spite of everything Shinji had done to her, he was still her brother, and she wouldn't wish the worms on anybody.

"Rider, please don't let them hurt him!"

Though Rider hated Shinji, her loyalty was to Sakura.

"As you wish, Master!"

Rider slashed away at the waves of worms, but they kept on coming. Zouken was most displeased.

"Sakura! You would dare stand against me!? Avenger, take Rider-"

Avenger wasn't listening. He was looking at Sakura and Rider's faces and body language. He could see the fear, disgust, and anger Sakura felt every time she interacted with Zouken, as well as Rider's desperation to keep Sakura and Shinji safe. Then he looked at Zouken and for the first time saw a soulless monster. In life, he did his best to avoid killing and to redeem everyone he faced, but he made a decision and drew his sword, facing Zouken.

"Fool, you cannot oppose me! My Command Spell forbids it!"

"I became a hero because I did whatever I felt was right, regardless of the rules. Besides, I cannot oppose you, but _this_ can!"

With that, he lopped his own right hand off at the wrist. It flew off with a spray of blood, but he grit his teeth and grunted; he had suffered far worse than this.

The others gasped, then realized they could now sense Avenger's presence and Zouken and Sakura could now see his stats. Then Zouken screamed and fell to his knees in agony as his prana was drained at an accelerated rate. If he had an ounce of compassion, he may have appreciated the irony in that this was similar to how Kariya met his end when Berserker unleashed Arondight. They could sense all that energy condensing around Avenger's stump, then the worms retreated in fear again.

"Losing Imagine Breaker is a necessary sacrifice to unleash my ultimate weapon! Feel honored to see my greatest Noble Phantasm! INVISIBLE DEMON!"

With so much dust in the air, Zouken and Sakura were terrified to see the outline of an invisible dragon's head emerge from Avenger's stump.

"Sic em!"

The dragon's neck extended and it roared before lunging at Zouken. In a panic, he raised his hand.

"By my Command Spe-"

He was cut off as the dragon swallowed him whole. His screams were cut off as his body was broken down into its component worms, then each worm was destroyed, one by one. In desperation, he attempted to transfer his consciousness into the worms scattered around the room, or the worms within Sakura's body, but found that his spirit was trapped within the dragon and slowly breaking down.

 _How can this be!? I have survived for so long! Will I really die right here, betrayed by my own Servant before I could even join the war!?_

They say dying can give a whole new perspective, and in Zouken Matou's final moments, he saw someone he had loved so long ago, allowing him to stop fighting his death and be at peace. It may have been more than he deserved, but even villains deserve some form of happiness.

 _Justeaze…_

As Sakura and Rider were amazed and a bit scared by what just happened, the worms in the room slowly died off now that their Master was dead. Avenger groaned as the dragon head slowly shrank down and went back inside his stump. He sheathed his sword, then picked up his right hand and held it to his stump, gritting his teeth and suppressing a scream as it healed up. He opened and closed his hand; good as new.

Suddenly, he staggered and fell to his knees, utterly exhausted. His body started fading away.

"Shit, I probably should have thought that through a bit more! Just my luck, I don't have Independent Action!"

With the death of his Master, his source of energy and his anchor to the world was gone. He turned to the girls. Rider instantly stood in front of Sakura in case he tried anything.

"Wait! I helped you out, so please help me! Girl, I can sense it. You have a lot of energy, more than enough to support more than one Servant. Please become my new Master!"

He rose and staggered towards them, but Rider held her blade to his throat and spoke in an icy whisper.

"Even if it was for a good cause, you betrayed your Master. How can we possibly trust you?"

Avenger searched his memory. In life, he was a slacker in school, not entirely his fault, as he was usually too busy saving the world, but after living so long, he had picked up a few things. With the knowledge the Holy Grail had given him only consisting of this era, he hoped his world was similar enough to this one.

"I had lived a full life with no regrets. I have no wish on the Grail and would like to return to my rest, but at the same time, I don't want to go just yet. If you agree to become my Master, I will do everything I can to protect you and help you win the Grail, and I will leave the wish to you. This I swear on my honor, on my blood, and on the River Styx!"

With the blood still on his hand, he knelt and wrote "I Promise" on the floor in kanji. Rider sighed and removed her blade. As a Greek anti hero, she understood his third oath perfectly.

"We can trust him, Master. He has performed a blood oath and an oath on the River Styx. Such a promise is unbreakable."

Sakura smiled.

"All right, let's be partners. Quick, before you disappear."

She walked toward him. He rose and tried to meet her halfway, but tripped and his face landed in Rider's bosom, and his left hand landed on Sakura's boob. Both girls (uncharacteristically in Rider's case) shrieked and shoved him away. However, Avenger sighed in relief as his body stabilized now that he had a Master again.

"I'm really sorry about that."

Now blushing, Rider crossed her arms.

"Just don't let it happen again."

"Heh, I only promise to try. Now that we are a team, we should get to know each other. In my experience, keeping secrets sucks. We need to know everything about each other if we are to work effectively."

"I guess I'll start. My name is Sakura Matou."

"That's a pretty name, Master. And who are you, Rider?"

Rider lowered her head, debating her options, before raising it.

"In life, I was known as Medusa, The Gorgon."

He raised an eyebrow.

"Wow. So that's why you wear a blindfold?"

"Yes."

"I've seen and heard of stranger things. In life, I was known as Touma Kamijou, He Who Purifies God And Exorcises The Devil. Nice to meet you. May we continue this conversation in someplace nicer, like upstairs?"

They agreed and started walking upstairs, Touma pausing to pick up the still unconscious Shinji and wondering what his Master would want to do with him.

Sakura observed her new Servant. He was amazing, having freed her from her two tormentors. She could tell by the way Rider was acting that she had a crush on him. She figured that if she wasn't already hopelessly in love with her senpai Shirou Emiya, she would have a crush on Avenger too.

She thought of the Holy Grail War, and could look forward to it with hope.

 **Author's Note:**

Servant Stat Sheet

Class: Avenger  
Master: Sakura Matou  
True Identity: Touma Kamijou (He Who Purifies God And Exorcises The Devil)

Alignment: Chaotic Good

Parameters:  
Strength: C+. In life, Touma is incredibly strong for a human. His punches can launch people through the air and make them make craters in concrete when they land. He blocked a punch from the concrete golem Ellis with one hand and when an iron cross the size of a car was thrown at him, he knocked it away with a backhand from his left arm. However, it is noted that he doesn't actually have super strength and he tends to fare badly if he tries to face opponents with super strength head on without a plan.

Endurance: A+. In life, he regularly jogs around the Academy without getting seriously winded and was able to race through London with an injured ankle. No matter how injured he is, he keeps fighting until he either wins or is knocked out.

Agility: B+ . In life, Touma can leap over twenty feet through the air and perform limited le parkour. Once, when a building was blown up, he was able to use the flying debris as stepping stones to go from ground level to reach the height of the fourth floor and grab a falling Kuroko Shirai who was inside the building. His reflexes are enough to block instantaneous attacks like Mikoto Misaka's electric attacks, and he once dodged a lightning strike from her while drunk. However, he doesn't have super speed and he tends to fare badly if he tries to face opponents with super speed head on without a plan.

Mana: B.

Luck: E-. Imagine Breaker completely negates his luck, except his luck with the ladies.

Skills:

Battle Continuation: A+. The ability to continue fighting in spite of injuries.

In life, Touma has powered through being beaten to a bloody pulp by martial artists and characters with super strength, getting electrocuted, getting shot, getting shrapnel in his left arm, and there goes without saying the sheer nightmarish torment Othinus put him through, which ended with him being reduced to nothing but a head, upper half of a torso, and right arm. He stayed alive long enough to convince her to turn good, at which point she restored him. It is possible to knock him unconscious, but those times are rare.

Charisma: C+. A person's charm as well as a natural ability to command and unify an army or country.

In life, Touma has an unconscious ability to bring people hope and turn them into heroes after fighting and/or talking to them, even if they used to be homicidal maniacs. Nearly all of his allies used to be his enemies. It's ranked low because he doesn't do it on purpose and is uninterested in becoming a leader.

Eye of the Mind (True): A. The ability to read and predict an opponent, honed from years of battlefield experience.

In life, Touma has learned how to find weaknesses and patterns in his opponents after fighting against street thugs, bullies, and superpowered enemies ever since he was a child.

Presence Detection: D. The ability to detect other Servants and local mana sources.

In life, Touma can detect mana, psychic energy, and divine energy. This skill is ranked low because it usually only activates when he is about to be attacked, though it does allow him to react to lightspeed or otherwise instantaneous attacks.

Kamiyan Disease: A. Almost all girls Touma interacts with, unless they are a lesbian or already attached to someone else, become attracted to him. They will inevitably fall in love with him after he rescues them. Touma also gains a + Stat Boost in all areas when fighting for or protecting girls.

In life, as long as they are attracted to men and have no significant other, no girl is immune to the Kamiyan Disease (an in-series nickname for Touma's ability to attract girls). Even Hyouka Kazakiri, an angel who was completely terrified of coming near him because his Imagine Breaker can kill her with one touch, and Othinus, a goddess who completely hated him at first, eventually fell in love with him. Kuroko Shirai, who is a lesbian and in love with Mikoto Misaka, dislikes Touma and continues to do so even after he saved her life.

Noble Phantasms:

Imagine Breaker: EX. This ability cannot be consciously deactivated, but does not consume prana. Contact with the right hand nullifies magic, psychic energy, and divine energy. Has no effect on the non supernatural, but this is mitigated by the fact Servants can only be harmed by supernatural attacks. Supernatural effects like energy blasts, curses, and artifacts shatter like glass and disintegrate on contact, unless they are continuously fed energy, but the right hand can touch them without being harmed and interact with them as if they are solid, allowing him to catch attacks and throw them back. Creatures not made of flesh like angels, psychic constructs, and Masterless Servants would shatter as well as they are not being fed energy. Superpowered beings touched by Imagine Breaker cannot activate their powers at all until he lets go. Touma cannot be detected by abilities that sense magical energy, but creatures at risk of being destroyed by Imagine Breaker feel an instinctual fear of it. Touma cannot be affected by teleportation, healing magic, telepathy, mind control, or alterations in the timeline or reality no matter where they touch his body, except via Command Spell. Imagine Breaker also drastically lowers his Luck stat. If the right arm is damaged or removed, it can heal nearly instantaneously, but this is painful and drains prana. There can be only one Imagine Breaker in the entire universe, so if Touma's right hand is severed and grows back, the original hand will disintegrate.

Touma was born with Imagine Breaker, which one of the greatest mysteries of his world as it doesn't make sense according to the laws of both science and magic. Some feats: While the sword of Archangel Michael is 40 km long and on fire, and too powerful to negate, Touma could catch and block it with his right hand without getting crushed or burned. When Touma punched Archangel Gabriel in the face, Gabriel disintegrated (the author clarified that Gabriel returned to Heaven, not cease to exist). When Rensa, who has the ability to copy other people's powers, attempted to copy Imagine Breaker, her arm blew up. When Othinus threw the spear Gungnir at him, which is undodgeable, unblockable, and cannot be shot down, Touma was able to punch it out of the air and destroy it, so he'd likely be able to do the same thing to Gae Bolg and Fragarach. While Imagine Breaker prevents him from being sensed, some of his enemies learned to detect him by looking for what seems to be a void in reality.

Invisible Demon: EX. This ability is sealed as long as Imagine Breaker is active. When Imagine Breaker is removed from Touma, an invisible dragon head of titanic but variable size emerges from the stump and targets his enemies. This dragon can only be harmed or defended against by EX or higher techniques. It only lasts a few minutes at most due to the massive prana consumption it requires. The dragon has its own mind and Touma must focus his will to recall it, though it will also recall itself if injured.

In life, the Invisible Demon's full power is difficult to gauge. It was more powerful than Fiamma of the Right, a man with the power of Archangel Michael who then temporarily attained the state La Persona Superiore A Dio, or The Person Higher Than God. When Mikoto Misaka was uncontrollably transforming into a angel, which was releasing so much energy it would have wiped out the city, the dragon swallowed her and spit her out normal. Later, Othinus, a gender flip version of Odin, effortlessly crushed it with one hand (it didn't die, it simply went back inside Touma) and said doing so was boring.

Whatever Works: D. Any object Touma holds becomes a D rank Noble Phantasm until thirty seconds after he lets go, allowing it to harm Servants. They can be held by Imagine Breaker without being negated.

In life, Touma uses a lot of improvised weapons, including shovels of cement power, a tube of grease, boiling coffee, a steel pipe, a power drill, and his own jacket. One time, he even tricked a teleporting opponent into materializing in the path of a train. If Whatever Works sounds like a rip off of Lancelot Berserker's Knight of Owner (Lancelot got this because he uses improvised weapons in his legend), it kinda is.


End file.
